Unless you're in the habit of purchasing bulk orders when you shop online, you can ditch the notion you are helping the environment by skipping a trip to the mall, a recent study has found. New research by The Institution of Engineering and Technology at Newcastle University shows online shoppers must order more than 25 items to have any less impact on the environment than traditional shopping due to resources required for shipping and handling. The study looked at "rebound" effects � or unintended side-effects of policies designed to reduce carbon emissions � of activities that are commonly thought to be green. Working from home is another commonly mistaken "green" activity, the study said. This practice actually increases home energy use by as much as 30%, and can lead to people moving further from the workplace, stretching urban sprawl and automobile use which increases pollution, the study said. "Policy makers must do their homework to ensure that rebound effects do not negate the positive benefits of their policy initiatives and simply move carbon emissions from one sector to another," said Professor Phil Blythe, Chair of the IET Transport Policy Panel and Professor of Intelligent Transport Systems at Newcastle University that produced the report. While the study focused on transportation issues in the UK, bringing the study to the U.S. could be beneficial for local policy planning, green technology website Green.blorge notes. "What works in New York City or Boston won't work for New Orleans or Jackson, Mississippi," the website says.